Bottom Line:
A cross-sectional survey was conducted in 360 children aged 5-18 years from six schools in Jimma Zone (southwest Ethiopia).For this STH, pools of 10 resulted in a significant underestimation of infection intensity.In this setting, the time in the laboratory was reduced by 70 % when pools of 5 instead of individual stool samples were screened.

Background: Our group has recently provided a proof-of-principle for the examination of pooled stool samples using McMaster technique as a strategy for the rapid assessment of intensity of soil-transmitted helminth infections (STH, Ascaris lumbricoides, Trichuris trichiura and hookworm). In the present study we evaluated this pooling strategy for the assessment of intensity of both STH and Schistosoma mansoni infections using the Kato-Katz technique.

Methods: A cross-sectional survey was conducted in 360 children aged 5-18 years from six schools in Jimma Zone (southwest Ethiopia). We performed faecal egg counts (FECs) in both individual and pooled samples (pools sizes of 5, 10 and 20) to estimate the number of eggs per gram of stool (EPG) using the Kato-Katz technique. We also assessed the time to screen both individual and pooled samples.

Results: Except for hookworms, there was a significant correlation (correlation coefficient = 0.53-0.95) between the mean of individual FECs and the FECs of pooled samples for A. lumbricoides, T. trichiura and S. mansoni, regardless of the pool size. Mean FEC were 2,596 EPG, 125 EPG, 47 EPG, and 41 EPG for A. lumbricoides, T. trichiura, S. mansoni and hookworm, respectively. There was no significant difference in FECs between the examination of individual and pooled stool samples, except for hookworms. For this STH, pools of 10 resulted in a significant underestimation of infection intensity. The total time to obtain individual FECs was 65 h 5 min. For pooled FECs, this was 19 h 12 min for pools of 5, 14 h 39 min for pools of 10 and 12 h 42 min for pools of 20.

Conclusions: The results indicate that pooling of stool sample holds also promise as a rapid assessment of infections intensity for STH and S. mansoni using the Kato-Katz technique. In this setting, the time in the laboratory was reduced by 70 % when pools of 5 instead of individual stool samples were screened.

Fig3: Agreement in faecal egg counts (FEC; expressed in eggs per gram of stool (EPG)) of soil-transmitted helminths between individual and pooled samples. Each of the 9 scatter plots represents the agreement in mean individual FEC and pooled FEC of stool samples. The plots in the first column represent Ascaris lumbricoides, second column Trichuris trichiura, and the third column hookworm. The plots in top, middle and bottom row represent pool sizes of 5, 10 and 20, respectively. The magnitude of correlation for each plot is based on the Pearson’s correlation coefficient (R)

Mentions:
The correlation in mean FEC of individual samples and the FEC of the pooled samples for the three pool sizes is illustrated in Fig. 3 for STHs and in Fig. 4 for S. mansoni. Overall, there was a significant positive correlation between mean FEC of individual samples and the FEC of the corresponding pooled samples for each of the three pool sizes for A. lumbricoides (RA. lumbricoides = 0.90–0.95, p < 0.01), T. trichiura (RT. trichiura = 0.52–0.72, p < 0.01) and S. mansoni (RS. mansoni = 0.66–0.75, p < 0.01). For hookworm, a positive correlation was found for each pool size, but only for a pool size of 5 the correlation was significantly different from zero (Rpool of 5 = 0.34, p < 0.01; Rpool of 10 = 0.19, p = 0.26; Rpool of 20 = 0.45, p = 0.06).Fig. 3

Fig3: Agreement in faecal egg counts (FEC; expressed in eggs per gram of stool (EPG)) of soil-transmitted helminths between individual and pooled samples. Each of the 9 scatter plots represents the agreement in mean individual FEC and pooled FEC of stool samples. The plots in the first column represent Ascaris lumbricoides, second column Trichuris trichiura, and the third column hookworm. The plots in top, middle and bottom row represent pool sizes of 5, 10 and 20, respectively. The magnitude of correlation for each plot is based on the Pearson’s correlation coefficient (R)

Mentions:
The correlation in mean FEC of individual samples and the FEC of the pooled samples for the three pool sizes is illustrated in Fig. 3 for STHs and in Fig. 4 for S. mansoni. Overall, there was a significant positive correlation between mean FEC of individual samples and the FEC of the corresponding pooled samples for each of the three pool sizes for A. lumbricoides (RA. lumbricoides = 0.90–0.95, p < 0.01), T. trichiura (RT. trichiura = 0.52–0.72, p < 0.01) and S. mansoni (RS. mansoni = 0.66–0.75, p < 0.01). For hookworm, a positive correlation was found for each pool size, but only for a pool size of 5 the correlation was significantly different from zero (Rpool of 5 = 0.34, p < 0.01; Rpool of 10 = 0.19, p = 0.26; Rpool of 20 = 0.45, p = 0.06).Fig. 3

Bottom Line:
A cross-sectional survey was conducted in 360 children aged 5-18 years from six schools in Jimma Zone (southwest Ethiopia).For this STH, pools of 10 resulted in a significant underestimation of infection intensity.In this setting, the time in the laboratory was reduced by 70 % when pools of 5 instead of individual stool samples were screened.

Background: Our group has recently provided a proof-of-principle for the examination of pooled stool samples using McMaster technique as a strategy for the rapid assessment of intensity of soil-transmitted helminth infections (STH, Ascaris lumbricoides, Trichuris trichiura and hookworm). In the present study we evaluated this pooling strategy for the assessment of intensity of both STH and Schistosoma mansoni infections using the Kato-Katz technique.

Methods: A cross-sectional survey was conducted in 360 children aged 5-18 years from six schools in Jimma Zone (southwest Ethiopia). We performed faecal egg counts (FECs) in both individual and pooled samples (pools sizes of 5, 10 and 20) to estimate the number of eggs per gram of stool (EPG) using the Kato-Katz technique. We also assessed the time to screen both individual and pooled samples.

Results: Except for hookworms, there was a significant correlation (correlation coefficient = 0.53-0.95) between the mean of individual FECs and the FECs of pooled samples for A. lumbricoides, T. trichiura and S. mansoni, regardless of the pool size. Mean FEC were 2,596 EPG, 125 EPG, 47 EPG, and 41 EPG for A. lumbricoides, T. trichiura, S. mansoni and hookworm, respectively. There was no significant difference in FECs between the examination of individual and pooled stool samples, except for hookworms. For this STH, pools of 10 resulted in a significant underestimation of infection intensity. The total time to obtain individual FECs was 65 h 5 min. For pooled FECs, this was 19 h 12 min for pools of 5, 14 h 39 min for pools of 10 and 12 h 42 min for pools of 20.

Conclusions: The results indicate that pooling of stool sample holds also promise as a rapid assessment of infections intensity for STH and S. mansoni using the Kato-Katz technique. In this setting, the time in the laboratory was reduced by 70 % when pools of 5 instead of individual stool samples were screened.